An air-to-air missile (AAM) is a guided missile fired from an aircraft for the purpose of destroying another aircraft. It is typically powered by one or more rocket motors, usually solid fuelled but sometimes liquid fuelled.
Guidance
Guided missiles operate by detecting their target (usually by either radar or infra-red methods, although rarely others such as laser guidance or optical tracking), and then “homing” in on the target on a collision course. The target is usually destroyed or damaged by means of an explosive warhead, often throwing out fragments to increase the lethal radius, typically detonated by a proximity fuse (or impact fuse if it scores a direct hit). Some missiles rely partially or wholly on their kinetic energy to damage the target, but almost all contain some kind of warhead, even if it is small. Note that although the missile may use radar or infra-red guidance to home on the target, this does not necessarily mean that the same means is used by the launching aircraft to detect and track the target before launch. Infra-red guided missiles can be “slaved” to an attack radar in order to find the target and radar-guided missiles can be launched at targets detected visually or via an infra-red search and track (IRST) system, although they may require the attack radar to illuminate the target during part or all of the missile interception itself.
Radar guidance is normally used for medium or long range missiles, where the infra-red signature of the target would be too faint for a infra-red detector to track. There are two major types of radar-guided missile – active and semi-active. Active radar-guided missiles carry their own radar system to detect and track their target. However, the size of the radar antenna is limited by the small diameter of missiles, limiting its range which typically means such missiles have to use another method to get close to the target before turning their radar set on, often inertial guidance). Semi-active missiles are simpler and more common. They function by detecting the reflection from the target of the launch aircraft’s own radar. This is also known as “beam-riding”. However, this means the launch aircraft has to remain a “lock” on the target, limiting its ability to manuever, which may be necessary should the target counter-attack. It also makes jamming the missile lock easier because the launching aircraft is further from the target than the missile, so the radar signal has to travel further and is greatly attenuated over the distance. Radar guided missiles can be countered by rapid maneuvering (which may result in them “breaking lock”, or may cause them to overshoot), deploying chaff or using electronic counter-measures.
Infrared guided missiles home in on the heat produced by an aircraft. Early infra-red detectors had poor sensitivity, so could only track the hot exhaust pipes of an aircraft. This meant an attacking aircraft had to manuever behind to a position behind its target before it could fire an infra-red guided missile. This also limited the range of the missile as the infra-red signature soon become too small to detect with increasing distance.
More modern infra-red guided missiles can detect the heat of an aircraft’s skin, warmed by the friction of airflow, in addition to the fainter heat signature of the engine when the aircraft is seen side-on or head-on. This, combined with greater maneuverability, gives them an “all-aspect” capability, and an attacking aircraft no longer had to be behind its target to fire, although launching from such a position typically increases the probability of a hit (however, the launching aircraft usually has to be closer in a tail-chase engagement).
An aircraft can defend against infra-red missiles by dropping flares that are hotter than the aircraft, so the missile homes in on the brighter, hotter target. Towed decoys and infra-red jammers can also be used. However, the latest missiles such as the ASRAAM use an “imaging” infra-red seeker which “sees” the target (much like a digital video camera), and can distinguish between an aircraft and a point heat source such as a flare. They also feature a very wide detection angle, so the attacking aircraft does not have to be pointing straight at the target for the missile to lock on. Instead, the pilot can use a helmet mounted display and target another aircraft by looking at it, and then firing. This is called “off-boresight” launch. In order to manuever sufficiently from a poor launch angle at short ranges in order to hit its target, missiles are now employing gas-dynamic flight control methods such as vectored thrust, which allow the missile to start turning “off the rail”, before its motor has accelerated it up to high enough speeds for its small aerodynamic surfaces to be useful.
Design
Air-to-air missiles are typically long, thin cyliners in order to reduce their cross section and thus drag at the very high speeds they typically travel at. At the front is the seeker, either a radar system, radar homer, or infra-red detector. Behind that lies the avionics which control the missile. Typically after that, in the centre of the missile, is the warhead, usually several kilogrammes of high explosive surrounded by metal that fragments on detonation (or in some cases, pre-fragmented metal). The rear part of the missile contains the propulsion system, usually a rocket of some type. Dual-thrust solid-fuel rockets are common, but some longer-range missiles use use liquid-fuel motors that can “throttle” to extend their range and preserve fuel for energy-intensive final manuevering. Some solid fuelled missiles mimic this technique with a second rocket motor which burns during the terminal homing phase. There are missiles in development, such as the MBDA Meteor, that “breathe” air (using a ramjet, similar to a jet engine) in order to extend their range. Modern missiles use “low-smoke” motors – early missiles produced thick smoke trails, which were easily seen be the crew of the target aircraft alerting them to the attack and helping them determine how to evade it.
List of air-to-air missiles
For each missile, short notes are given, including an indication of its range and guidance mechanism.
France:
Matra Magic R.550 – IR guided missile, similar to the American Sidewinder.
Matra Magic II – IR guided missile.
Magic Super 530F/Super 530D – French couterpart of the AIM-7 Sparrow.
MBDA Mica – French counterpart of the AMRAAM missile.
Germany:
X-4 missile – WW2 design, MCLOS, never saw service
International:
Alenia Aspide – Italian manufactured version of the AIM-7 Sparrow.
MBDA Meteor – medium range, active radar; design to replace AMRAAM
IRIS-T – short range IR; replacement for Sidewinder
Israel:
Rafael Shafrir –
Rafael Shafrir 2 –
Rafael Python 3 –
Rafael Python 4 – medium range IR
Rafael Python 5 – medium range IR; improves on Python 4
Rafael Derby –
People’s Republic of China
PL-1 – Chinese version of the Soviet AA-1
PL-2 – PRC version of the AA-2
PL-3 – updated PRC version of the AA-2
PL-5 – updated PRC version of the AA-2
PL-7 – PRC version of the French Magic
PL-8 – PRC version of the Israeli Python 3
PL-9 – short range IR guided missile
PL-10 – semi-active radar guided medium range PRC version of the Italian Aspide
PL-11 / AMR-1 – similar to the Russian AA-10 with active homing guidance system.
TY-90 – first air-to-air missile solely designed for helicopters.
Russia/USSR:
K-5 missile (AA-1 Alkali) – beam-riding
K-13 missile (AA-2 Atoll) – short-range IR or SARH
K-8 missile (AA-3 Anab) – IR or SARH
K-9 missile (AA-4 Awl) – IR or SARH
R-4 missile (AA-5 Ash) – IR or SARH
R-40 missile (AA-6 Acrid) – long-range IR or SARH
R-23 missile (AA-7 Apex) – medium-range SARAH or IR
R-60 missile (AA-8 Aphid) – short-range IR
R-33 missile (AA-9 Amos) – long range active radar
R-27 missile (AA-10 Alamo) – medium-range SARH or IR
R-73 missile (AA-11 Archer) – short-range IR
R-77 missile (AA-12 Adder) – medium-range active radar
UK:
AIM-132 ASRAAM – short range IR
Skyflash – medium-range radar-guided carried by RAF interceptors.
USA:
AIM-4 Falcon – operational guided
AIM-7 Sparrow – medium range semi-active radar
AIM-9 Sidewinder – short range IR
AIM-54 Phoenix – long range, semi-active and active radar
AIM-120 AMRAAM – medium range, active radar; replaces Sparrow
AIR-2 Genie – air-to-air rocket with 1.5-2 kiloton nuclear warhead – was in service 1957 – 1985.
